The XSF organizes periodic in-person gatherings in order to coordinate high-bandwidth conversations, interop testing, brainstorming and planning, and to conduct other XSF business face-to-face.
Summit 19 will be held once again in Brussels in February 2016, in tandem with FOSDEM.
The last event was the US XMPP Summit in Richland, WA in October. Prior to that, Summit 17 was the European XMPP Summit, held in coordination with FOSDEM in Brussels.
XSF members and other XMPP developers can be found at events regularly all over the world.
If you're speaking about XMPP at an upcoming event, please add them to the list and submit it to Lanyrd.